In this paper, we first study the skew cyclic codes of length ps over R3 = Fpm + uFpm + u2Fpm, where p is a prime number and u3 = 0. Then we characterize the algebraic structure of FpmFpm[u2]-additive skew cyclic codes of length 2ps. We will show that there are sixteen different types of these codes and classify them in terms of their generators.